Cause of East Coast Dolphin Die-Off Found

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Federal scientists say a virus related to human measles is likely
to blame for the mass die-off of bottlenose dolphins along the
East Coast. Based on the last outbreak, they say it could affect
the species until next year.

Since July 1, the National Oceanic and Atmospheric
Administration (NOAA) says 333 dead or sickly
bottlenose dolphins have washed up from North Carolina to New
York. That's over nine times the historical average for
strandings during this period. The bulk of those reports — 174 of
them — have come from Virginia.

NOAA officials had already declared it an "unusual mortality
event" and had been taking samples from dead dolphins to
investigate the cause. So far, 32 of 33 samples tested for
morbillivirus were either suspect (25 cases) or confirmed
positive (seven cases), researchers with the agency told
reporters Tuesday (Aug. 27). [ 10
Deadly Diseases That Hopped Across Species ]

Dolphin morbillivirus is related to other morbilliviruses
that can cause measles in people or canine distemper in dogs, but
the pathogens are unlikely to spill over to other species.
Bottlenose dolphins catch the disease through direct contact with
infected dolphins and respiratory particles, or those particles
that travel through the respiratory tract from the air dolphins
breathe. Infected animals may develop lesions, brain infections
and pneumonia, as well as secondary bacterial, viral and/or
fungal infections.

The same disease caused a deadly outbreak 26 years ago when more
than 700 dead bottlenose dolphins were found from New Jersey to
Florida between June 1987 and May 1988.

"We're expecting that if indeed this plays out the way that
die-off occurred that we're looking at mortalities being higher
and the moribillivirus spreading southward and likely continuing
until spring of 2014," Teri Rowles, National Marine Mammal
Stranding Coordinator with NOAA Fisheries, said during
a conference call today (Aug. 27).

Researchers suspect this summer's rash of morbillivirus began
with a young population that was born after the 1987/1988
outbreak and had no natural defenses against the disease.

"Many of the dolphins younger than 26 years old have limited to
no immunity to this virus," Rowles
said. "So if the virus is introduced, they don't have the
traditional antibodies to protect them."

That also means as the outbreak progresses, the dolphins that
survive will build up immunity, and the number of strandings
should hopefully decrease.

"It will probably end when the number of susceptible animals
dwindles," virologist Jerry Saliki, of the University of Georgia,
told reporters. "Not all infected animals will die. As the
outbreak proceeds, the number of immune animals will increase."

As they continue to monitor the outbreak, the researchers say
they are investigating other factors that may have made the
animals more susceptible to the virus. Rowles said they will test
for contaminants to see if dolphins with high levels of
polychlorinated biphenyls (PCBs) or other man-made toxins
were affected more severely.